Unmanned Aerial Vehicles (UAVs) have been in military service for decades, under various designations: drones, RPVs, RPAs, UASs, and UCAVs. They perform a variety of roles with both non-lethal and lethal payloads: reconnaissance, signals/intelligence gathering, persistent surveillance and strike/attack. They are especially useful for missions which are dangerous and would stretch an onboard human pilot's endurance, or which are not worth risking the pilot's life.
Without a human pilot on board, the UAV's limitations essentially come down to its range/payload. Although some UAVs such as the RQ-4 Global Hawk have very impressive range and endurance, most combat-intended UCAV (unmanned combat aerial vehicle) designs have much shorter range. Aerial refuelling has long been used to extend an aircraft's range, but it has been the nearly-exclusive preserve of manned aircraft. Only recently have the first trials been carried out that demonstrated the feasibility of UAVs to aerial refuel autonomously, and this capability will become commonplace in future.
For those UAVs with aerial refuelling capability and disposal payloads, i.e. ordnance, their last remaining limitation therefore becomes that of payload: once they have expended their ordnance, the UAVs must return to base to rearm, which may be many miles/hours of transit away. A potential need therefore exists, for a system that can retrieve UAVs in mid-flight, bring them aboard a servicing aircraft to refuel and rearm them, and re-release them in flight to continue with their mission, without the need for the UAVs to transit to/from their base.
There have been several historical programs aimed at extending the range/endurance of small (both manned and unmanned) aircraft, other than through aerial refuelling. In the late 1940's-early 1950's, the US Air Force (USAF) experimented with several concepts, including the “parasite fighter”: a tiny fighter carried in the bomb bay of a bomber; the wing-tip attachment Projects Tip Tow and Tom-Tom; and the fighter conveyor (FICON) concept: a normal-sized fighter carried in the bomb bay of a very large bomber. When aerial refuelling capability became commonplace, all these concepts were abandoned.
A “mothership” concept that did become operational was the DC-130 drone controller program. In the mid 1960's-early 1970's, the USAF operated specially-equipped C-130 Hercules transports to launch Firebee/Lightning Bug drones from under wing pylons; after the drones completed their missions, they flew on to the recovery area, deployed a parachute and were retrieved in flight by helicopters. This concept employed different launch and recovery platforms, and there was no capability to refuel/rearm the drones in flight, which still had to be done back at base.
In the early 1970s′, the USAF revisited the mothership concept again by commissioning the Boeing Aerospace Company to develop the micro-fighter/airborne aircraft carrier concept. The concept envisages the development of small manned “micro-fighters” capable of being carried in multiples aboard a large transport/cargo aircraft such as the Boeing 747 or Lockheed C-5. The micro-fighters are stowed in the cargo hold of the mothership, can be armed/fuelled, and their pilots can enter/exit the cockpits in flight. To launch the micro fighter, it is moved into position by a conveyor system over the launch bay. The launch bay inner pressure doors open and a mechanical trapeze arm system swings into position above the wings of the fighter and latches onto the attachment points. The arm lowers the fighter into the launch bay, after which the pressure doors close. The bay is then de-pressurised, the outer doors opened, and the trapeze lowers the fighter into the airstream where it is released. To retrieve the fighter in flight, it flies into formation with the mothership, where a refuelling boom extends to engage the receptacle of the fighter. The boom then maneuvers the fighter into the engagement envelope of the trapeze arm, which latches onto the attachment points. The fighter is then brought aboard in a reverse of the procedure described above. This Boeing concept comes closest to providing a “full service” capability in flight: enabling refuelling, rearming and even crew changes. However, it is wholly dependent on purpose-designed and built micro-fighters; and purpose-built variants of albeit existing transport/cargo aircraft designs, and would be impractical and cost-prohibitive to implement with an air force's existing fleet.
Two more recent concepts have been proposed by the USAF, and by FAR Technologies of Israel. In U.S. Pat. No. 6,932,299 B2, “Apparatus for aerial rearmament of aircraft” and U.S. Pat. No. 7,793,888, “Apparatus and method for air-to-air arming of aerial vehicles”, they propose broadly similar concepts are disclosed that involve a transport aircraft extending a rigid telescopic boom, on which the ordnance transfer/loading device is conveyed to the recipient aircraft, formatting on the transport. In both concepts, the recipient aircraft is rearmed while flying in close formation with the transport aircraft, and the rearming is possible only with aircraft fitted with stores on external pylons (which are exposed and thus more easily “accessible”); they do not appear to have the capability to rearm aircraft equipped with internal weapons bays.
Both concepts also appear to be for rearming only and no refuelling; therefore if refuelling is required as well, the recipient aircraft would have to engage the tanker aircraft in a separate aerial refuelling procedure, which would extend the overall rearming/refuelling operation time. Similarly, both concepts do not allow for “basic maintenance” to be performed on the recipient aircraft in flight, e.g. the replacement of faulty avionics line-replaceable units (LRUs).
A need therefore exists to provide an apparatus and method for aerial recovery of an unmanned aerial vehicle that seeks to address at least some of the above problems.